For millions of PC users, the privacy-snatching programs known as spyware have been nothing but a headache as they swipe personal information, slow systems to a crawl and crash computers.

For Webroot Software Inc., the annoying programs have been the foundation of success. Thanks to its market-leading anti-spyware software, Spy Sweeper, sales have soared 20-fold since 2002, and last year the privately held company raised an eye-popping $108 million in venture capital.

Though there's little chance of spyware ever going away, Webroot is facing a significant challenge in the coming years: Microsoft Corp.'s upcoming Windows Vista operating system will include its own spyware-squashing tools.

Vista could put Webroot in the same shoes as RealNetworks Inc., Netscape Communications Corp. and others whose businesses have suffered after Microsoft bundled more features into its ubiquitous operating system.

Still, Webroot CEO David Moll seems unfazed.

"The taking of a second-best product in this space is akin to locking half the doors in your house," he said. "Vista will not solve the spyware problem. It may change the vector of attack, but it will not solve this problem. And I'll bet the company on it."

Some analysts say the company should broaden its focus - and Moll, without divulging details, said that's in the plans.

"Ultimately they need to offer more than just an anti-spyware package," Yankee Group senior analyst Andrew Jaquith said. "To do that, they need access to more money, or be part of a bigger company."

Moll said he expects 20 percent revenue growth this year, while Jaquith estimates current overall annual revenue at $75 million to $110 million. Jaquith said an initial public offering is more likely than a buyout because, he estimates, it could take $500 million to acquire the company - a sum he figured few rivals would be willing to pay.

Although an initial public offering isn't imminent, Moll said, Webroot is implementing some of the financial controls required for public companies.